How can I add GtkEventBox in scrolled windows layout? - c

Question

I have a GTK+2 program which combining GtkScrolledWindow and GtkLayout. It works fine. But, I found if I put a GtkEvent object to GtkLayout, it will not display properly. Anybody knows why ? Thanks.
#include <gtk/gtk.h>
int main( int argc, char *argv[] )
{
GtkWidget *window, *button, *layout, *eventbox, *scrollwindow;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_widget_set_size_request (window, 150, 150);
button = gtk_button_new_with_label ("button");
layout = gtk_layout_new(NULL, NULL);
gtk_layout_set_size( GTK_LAYOUT(layout), 300, 300);
scrollwindow = gtk_scrolled_window_new(GTK_LAYOUT(layout)->hadjustment, GTK_LAYOUT(layout)->vadjustment);
gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (scrollwindow), GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);
gtk_layout_put( GTK_LAYOUT(layout), button, 50, 250 );
/* uncomment to use eventbox
eventbox = gtk_event_box_new();
gtk_container_add( GTK_CONTAINER(eventbox), layout);
gtk_scrolled_window_add_with_viewport( GTK_SCROLLED_WINDOW(scrollwindow), eventbox);
*/
// comment this line when use eventbox
gtk_container_add( GTK_CONTAINER(scrollwindow), layout);
gtk_container_add((GtkContainer*)window, scrollwindow);
gtk_widget_show_all(window);
gtk_main ();
return 0;
}
The picture if the eventbox is used.

Answer 1

I found it does not have to use GtkEventBox here. The GtkLayout can capture events directly.
The following widgets do not have an associated window. So, It should be used with the GtkEventBox if you want to capture events.
GtkAlignment
GtkArrow
GtkBin
GtkBox
GtkImage
GtkItem
GtkLabel
GtkPaned
GtkPixmap
GtkScrolledWindow
GtkSeparator
GtkTable
GtkViewport
GtkAspectFrame
GtkFrame
GtkVPaned
GtkHPaned
GtkVBox
GtkHBox
GtkVSeparator
GtkHSeparator
The fixed program :
#include <gtk/gtk.h>
static gboolean button_press_event( GtkWidget *widget, GdkEventButton *event ) {
if (event->button == 1 ) printf("but down %i , %i\n", (int)event->x, (int)event->y);
return TRUE;
}
int main( int argc, char *argv[] )
{
GtkWidget *window, *button, *layout, *eventbox, *scrollwindow;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_widget_set_size_request (window, 150, 150);
button = gtk_button_new_with_label ("button");
layout = gtk_layout_new(NULL, NULL);
gtk_layout_set_size( GTK_LAYOUT(layout), 300, 300);
scrollwindow = gtk_scrolled_window_new(gtk_layout_get_hadjustment(layout), gtk_layout_get_vadjustment(layout));
gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (scrollwindow), GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);
gtk_layout_put( GTK_LAYOUT(layout), button, 50, 250 );
gtk_container_add( GTK_CONTAINER(scrollwindow), layout);
gtk_container_add(GTK_CONTAINER(window), scrollwindow);
g_signal_connect (layout, "button_press_event", G_CALLBACK (button_press_event), NULL);
gtk_widget_set_events(layout, GDK_EXPOSURE_MASK
| GDK_LEAVE_NOTIFY_MASK | GDK_BUTTON_PRESS_MASK
| GDK_POINTER_MOTION_MASK | GDK_POINTER_MOTION_HINT_MASK);
gtk_widget_show_all(window);
gtk_main ();
return 0;
}
The result of clicking on GtkLayout :